Granddad's Japanese Sword - Fake?

Article about: My grandmother just recently died, and with my grandfather dead several years before, we began to go through their belongings. In the attic, we found two Japanese-looking swords. My father s

Granddad's Japanese Sword - Fake?

My grandmother just recently died, and with my grandfather dead several years before, we began to go through their belongings. In the attic, we found two Japanese-looking swords. My father said that my grandfather got them in WWII, in Japan.

There's one that I'm fairly sure is fake. The hilt is a stylized dark green demon head, which, with my extremely limited knowledge of swords, I'm assuming would not be used on a military sword. It had no scabbard, and the blade was in bad shape, with rust and such.

The other sword I'm not so sure of. It came in a scabbard, with chipped olive green paint, and a matching D-ring on the side. The sword itself locked into the scabbard such that you had to press in a ~2 inch long thin strip of metal to take it out. The sword was perhaps 3 feet long, in surprisingly good repair. It had a groove near the back. The two elements that seem somewhat fake are the plastic-y hilt, made with a braided-like motif in olive green and tan, I think. Also, on the side of the blade, between the back and the groove, there is a 5-digit serial number, in American numerals, and a similar serial number was on the top of the scabbard, where the paint has chipped away.

My grandfather was stationed in the Pacific theater. I've asked several members of my family, and none of them can provide more detail than that. I don't even know if he saw combat. I'm currently in the process of looking up his service records.

I'm sorry that my info is so sketchy. I'm writing from memory, and will update with photos, serial numbers, and more details as soon as possible.

I'd like to know anything that anyone could tell me about these two swords. Were either actually likely Japanese? Where did they come from? How did my grandfather likely come by them? Any info at all is helpful.